The flutter is shaped like a pipe with a steel ball on a cone inside. You must hold the flutter at the right angle to make it work. Blowing into the mouthpiece makes the steel ball rise and fall. Breathing into the flutter sends vibrations throughout your child's lungs that help loosen the trapped mucus. Blowing harder and faster into the mouthpiece helps shake loose the mucus and moves it up and out of his or her lungs.